There is a clear need for a low cost, network manageable, advanced gas sensor for sulfur hexafluoride gas (SF6) used in high voltage electric switchgear. SF6 plays a crucial arc-suppression role in this equipment. An expensive commodity and a potent greenhouse gas (GWP 23,900 times that of CO2), SF6 lost through leakage is a costly problem justifying an effective monitoring system. The instant invention appreciates the application requirements and the sensor and communications network technologies required to meet them. The invention further supports security aspects that are paramount and tolerates the outdoor substation application environment which is challenging.
Worldwide, of 7 million kg of SF6 produced annually, most (˜75% or 5.5 metric tones per annum) is used for electric power equipment. Consequences for the environment and cost implications for electrical energy producers and users are clearly conveyed. Lower-impact, lower-cost alternatives to SF6, though sought, are not found. Techniques for estimating emissions have been based predominately upon indirect, mass-balance accounting methods that are costly and error-prone. Trials using expensive equipment (e.g. IR camera) combined with substantial labor have nonetheless shown that environmental impacts and gas expense arising from leakage are significant and can be reduced.
Presently, SF6 contributes 3% CO2-equivalent emissions. As global electric usage (3×106 Wh/capita) ascends to U.S. levels (1.3×107 Wh/capita), global generation increases 5-fold. While CO2 emission per kWh generated must surely decrease, SF6 emissions will scale with distribution. Switchgear equipment manufacturers and utilities need a low cost, network manageable, advanced gas sensor to achieve reductions in SF6 emissions per kWh.
All electric producers and users benefit. The instant invention targets economical, distributed sensor technology that can be applied worldwide to achieve a 100-fold reduction in emissions rate—a tremendous opportunity for the environment and economies worldwide.
References Cited and incorporated herein by reference hereto in their entirety follow:
[1] United States Environmental Protection Agency, “Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2008”, Washington, D.C., Apr. 15, 2010.
[2] Debra Knopman, Katie Smythe, “2004-2006 SF6 Data Summary”, PM-2327-NEMA, June, 2007, Prepared for the National Electrical Manufacturers Association.
[3] United States Environmental Protection Agency, “SF6 Emission Reduction Partnership for Electric Power Systems—2007 Annual Report”, Washington, D.C., December, 2008.
[4] Jos Olivier, Joost Bakker, Jan Willem Wouda, Rainer Bitsch, and Manfred Maiss, “Global Emission Sources of Greenhouse Gas Emissions from Industrial Processes: SF6”, IPCC Task Force on National Greenhouse Gas Inventories, January, 2003.
[5] L. G. Christophorou, J. K. Olthoff, and D. S. Green, “Gases for Electrical Insulation and Arc Interruption: Possible Present and Future Alternatives to Pure SF6”, NIST Technical Note 1425, November, 1997.
[6] United States Environmental Protection Agency, “Electric Transmission and Distribution Equipment Use—Final Rule: Mandatory Reporting of Greenhouse Gases (40 CFR 98, Subpart DD)”, November, 2010.
[7] Alfieri, M. 2002. “Partner Case Study: Con Edison”, Presented on behalf of Con Edison at the International Conference on SF6 and the Environment: Emission Reduction Strategies. San Diego, Calif., Nov. 21-22, 2002.
[8] Robert Madding and Robert Benson, “Detecting SF6 Insulating Gas Leaks with an IR Imaging Camera”, Electricity Today, pp. 12-15, November/December, 2007.
[9] Jan-Martin Rhiemenier, Sina Wartmann, Marcello Pagnotta, Natalia Makowska, and Xingyu Li, “Update on global SF6 Emissions trends from electrical equipment—Edition 1.1”, Ecofys Germany GmbH, July, 2010.
[10] U.S. Department of Energy, “U.S. Energy Information Administration Electric Power Annual 2009”, Washington, D.C., November, 2010.
[11] WIKA Alexander Wiegand GmbH & Co. KG, “Gas Density Monitor (GDM) with Integrated Gas Density Transmitter, Model 233.52.100 TI”, Klingenberg, Germany, May, 2009.
[12] J. Blackman, M. Averyt, and Z. Taylor, “SF6 Leak Rates from High Voltage Circuit Breakers—U.S. EPA Investigates Potential Greenhouse Gas Emissions Source”, presented at the International Conference on SF6 and the Environment: Electric Power Systems—Partnership Update, Nov. 28, 2006.
[13] General Electric Company, “72.5 kV Circuit Breakers Data Sheet”, Nov. 10, 1999.
[14] General Electric Company, “121 kV Circuit Breakers Data Sheet”, Mar. 1, 2002.
[15] General Electric Company, “145 kV Circuit Breakers Data Sheet”, Nov. 10, 1999.
[17] General Electric Company, “169 kV Circuit Breakers Data Sheet”, Nov. 10, 199.
[18] General Electric Company, “242 kV Circuit Breakers Data Sheet”, Nov. 10, 1999.
[19] General Electric Company, “362 kV Circuit Breakers Data Sheet”, Nov. 10, 1999.
[20] General Electric Company, “550 kV Circuit Breakers Data Sheet”, Nov. 10, 1999.
[21] Solon Manufacturing Company, “2TC, SF Gas Density Switch, Intrinsic Gauge Design”, Chardon, Ohio.
[21] Giancarlo Scalabrin, Luigi Bettio, Paolo Marchi, and Paolo Stringari, “A Fundamental Equation of State for Sulfur Hexafluoride (SF6) in Extended Equation of State Format”, JPCRD 36(2) pp. 617-662, 2007.
[22] Maryland Department of the Environment, “Maryland CO2 Budget Trading Program, COMAR 26.09.03”, Baltimore, Md., August, 2009.
[23] California Environmental Protection Agency, Air Resources Board, “Proposed Regulation Order: Regulation for Reducing Sulfur Hexafluoride Emissions from Gas Insulated Switchgear”, Sacramento, Calif., Jan. 7, 2010.
[24] United Nations Framework Convention on Climate Change, “SF6 Emission Reductions in Electrical Grids”, Bonn, Germany, Sep. 29, 2006.
[25] United States Department of the Interior Bureau of Reclamation, “Management and Safe Handling Procedures for Sulfur Hexaflouride (SF6) Gas”, March, 2004.
Each of the foregoing references is included with an information disclosure statement filed contemporaneously with the filing of the instant patent application.